Dude, those are major point releases. Those are complete rebuilds of every package from source. Plus testing. That's a hell of a lot of difference than how long a single patch takes to make it through. Also, critical patches issued during that period bypass the process and are pushed out immediately. The only thing that is lagging is that Red Hat has gone SO long between RHEL 5 and 6. But RHEL 6 is going to have a heck of a lot of major changes from 5. Many major subsystems were replaced since RHEL 5.